Field of the Invention
The disclosed and claimed concept relates to a circuit breaker and, more specifically, to a circuit breaker operating mechanism that is structured to resist rebounding from an open, first configuration to a closed, second configuration.
Background Information
Electrical switching apparatus include, for example, circuit switching devices, circuit interrupters, such as circuit breakers, network protectors, contactors, motor starters, motor controllers, and other load controllers. Electrical switching apparatus such as circuit interrupters and, in particular, circuit breakers are well known in the art. Circuit breakers are used to protect electrical circuitry from damage due to an over-current condition, such as an overload condition or a relatively high level short circuit or fault condition. Circuit breakers typically include a number of pairs of separable contacts, an operating mechanism, and a trip unit. The separable contacts move between on open, first configuration and a closed, second configuration. The separable contacts may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to an over-current condition.
That is, the operating mechanism is designed to rapidly open and close the separable contacts. In an exemplary embodiment, the operating mechanism includes a number of linkage members and biasing elements. The linkage members move between an open, first configuration and a closed, second configuration (which correspond to the configuration of the contacts). The biasing elements bias the linkage members, and therefore the operating mechanism and contacts, to the first open configuration. The operating mechanism is structured to be latched and thereby maintain the contacts in a closed, second configuration. The trip unit is structured to detect over-current conditions. When an over-current condition is detected, the trip unit, and in an exemplary embodiment, a trip bar releases the operating mechanism latch thereby allowing the biasing elements to bias the linkage members, and therefore the operating mechanism and contacts, to the first open configuration. After such an event, and in an exemplary embodiment, the operating mechanism, as well as the trip unit, are moved into a reset configuration wherein elements are positioned and the biasing elements charged in preparation for returning to the second configuration.
A disadvantage of such circuit breakers is that the elements of the operating mechanism and the trip assembly move so rapidly that, upon reaching the first configuration, momentum and elastic forces cause certain elements to rebound, that is, bounce back toward the second configuration. The rebound motion can position various elements in a configuration that interfere with the reset configuration. There is, therefore, a need for an operating mechanism for a circuit breaker that substantially arrests the reverse motion of the linkage members after an over-current event. There is a further need for a such an operating mechanism to be incorporated into existing circuit breakers.